252 Mr. Delaval on the Cauje of the 



do not vary the fpecies of their colour, but only 

 tranfmit a diluter, or more intenfe red. 



Nor do red glafles appear yellow, or orange, 

 when divided into the thinneft plates. 



Thefe Tranfparent Red Media, from the 

 interception of the tranfmitted rays, fuffer no 

 other change, except the diminution, or lofs, of 

 their colour, whereby they aflume a darker hue, 

 or become black. 



As the changes of colour, thus efFefted in 

 yellow liquors, have been already obferved, I 

 ihall not mention any experiments relative to 

 them, but Ihall advert to other media, whofe 

 phsenomena have not, I believe, been hitherto 

 noticed. 



I digefted, in fpirit of wine, a fufficient quan- 

 tity of lap green, which is an exprefled vegetable 

 juice, infpiffated, and dried. When the fpirit of 

 wine was faturated with this colouring fubftancc, 

 it was filtered through paper, and afterwards 

 poured into a fmall flint- glafs bottle which was 

 of the form of a wedge, or triangular prifm. 



That portion of the coloured liquor, which 

 was contained in the angular part of the bottle, 

 and which, confequently was the thinneft, 

 tranfmitted a vivid green colour ; that portion, 

 which was in the wideft part of the bottle, tranf- 

 mitted a bright red colour ; the intermediate 

 portion, which was between the green and the 

 j-ed, tranfmitted a yellow colour; but the yellow 



W4S 



